9 research outputs found

    Effects of halo substructure on the power spectrum and bispectrum

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    We study the effects of halo substructure and a distribution in the concentration parameter of haloes on large-scale structure statistics. The effects on the power spectrum and bispectrum are studied on the smallest scales accessible from future surveys. We compare halo-model predictions with results based on N-body simulations, but also extend our predictions to 10-kpc scales which will be probed by future simulations. We find that weak-lensing surveys proposed for the coming decade can probe the power spectrum on small enough scales to detect substructure in massive haloes. We discuss the prospects of constraining the mass fraction in substructure in view of partial degeneracies with parameters such as the tilt and running of the primordial power spectrum.Comment: 9 pages, 10 figures; replaced with version published in MNRAS; removed grey-scale versions of figures which were being included at the end by the serve

    Baryon Oscillations and Dark-Energy Constraints from Imaging Surveys

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    Baryonic oscillations in the galaxy power spectrum have been studied as a way of probing dark-energy models. While most studies have focused on spectroscopic surveys at high redshift, large multi-color imaging surveys have already been planned for the near future. In view of this, we study the prospects for measuring baryonic oscillations from angular statistics of galaxies binned using photometric redshifts. We use the galaxy bispectrum in addition to the power spectrum; this allows us to measure and marginalize over possibly complex galaxy bias mechanisms to get robust cosmological constraints. In our parameter estimation we allow for a weakly nonlinear biasing scheme that may evolve with redshift by two bias parameters in each of ten redshift bins. We find that a multi-color imaging survey that probes redshifts beyond one can give interesting constraints on dark-energy parameters. In addition, the shape of the primordial power spectrum can be measured to better accuracy than with the CMB alone. We explore the impact of survey depth, area, and calibration errors in the photometric redshifts on dark-energy constraints.Comment: 17 pages, 12 figure

    Dark energy and substructure effects on the large -scale structure

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    I consider in detail how the large-scale structure of the universe can provide information about two topics of current interest in cosmology: the nature of dark energy and the abundance of substructure in dark matter halos. Baryonic oscillations in the galaxy power spectrum have been studied as a way of probing dark energy models. While most studies have focused on spectroscopic surveys at high redshift, large multicolor imaging surveys have already been planned for the near future. In view of this, I consider the prospects for measuring baryonic oscillations from angular statistics of galaxies binned using photometric redshifts. I use the galaxy bispectrum in addition to the power spectrum; this allows one to measure and marginalize over possibly complex galaxy bias mechanisms to get robust cosmological constraints. I find that a multicolor imaging survey that probes redshifts beyond unity can give interesting constraints on dark energy parameters. In addition, the shape of the primordial power spectrum can be measured to better accuracy than with the cosmic microwave background alone. In the second example I consider the effects of halo substructure on large-scale structure statistics. The effects on the power spectrum and bispectrum are studied on the smallest scales accessible from future surveys. We compare halo model predictions with results based on N-body simulations, but also extend our predictions to 10 kpc scales which will be probed by future simulations. We find that weak-lensing surveys proposed for the coming decade can probe the power spectrum on small enough scales to detect substructure in massive haloes. We discuss the prospects of constraining the mass fraction in substructure in view of partial degeneracies with parameters such as the tilt and running of the primordial power spectrum

    Universal Solvation Model Based on Conductor-Like Screening Model

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    ABSTRACT: Atomic surface tensions are parameterized for use with solvation models in which the electrostatic part of the calculation is based on the conductor-like screening model (COSMO) and the semiempirical molecular orbital methods AM1, PM3, and MNDO/d. The convergence of the calculated polarization free energies with respect to the numerical parameters of the electrostatic calculations is first examined. The accuracy and precision of the calculated values are improved significantly by adjusting two parameters that control the segmentation of the solvent-accessible surface that is used for the calculations. The accuracy of COSMO calculations is further improved by adopting an optimized set of empirical electrostatic atomic radii. Finally, the electrostatic calculation is combined with SM5-type atomic surface tension functionals that are used to compute the nonelectrostatic portions of the solvation free energy. All parameterizations are carried out using rigid (R) gas-phase geometries; this combination (SM5-type surface tensions, COSMO electrostatics, and rigid geometries) is called SM5CR. Six air–water and 76 water–solven
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